Humidity control



Oct. 3l, 1950 E. B. JANVRIN HUMIDITY CONTROL Filed March l, 1946 FIG.I

IN VEN TOR.

Patented Oct. 31, 1950 UNITED STATES PATENT oFFrcE HUMIDITY CONTROL Everett B. Janvrin, Cincinnati, Ohio, assignor t TheBristol Company, Waterbury, Conn., a corporation of Connecticut Application March 1, 1946, Serial N0. 651,128

4 Claims.

This invention relates to humidity controlling devices, and more especially to a method and means for regulating the moisture content of a stream of air or other gaseous medium in an enclosed conduit. In many industrial processes, it is desired that a flowing gas be maintained at a predetermined value of relative humidity, even though its temperature vary through a considerable range, and that such regulation be eifected quickly and positively. Furthermore, it may be desired to maintain a certain value of relative humidity at one time, and an entirely different value at another time, and to change from one value to another with a minimum of delay.

It is an object of the present invention to provide means whereby temperature readings simultaneously performed by dryand wet-bulb thermometer elements exposed to an atmosphere whose moisture content is to be regulated may be caused to exercise their joint influence in maintaining said moisture content at a desired pre- Y determined value.

I t is a further object to provide means of the above nature in which a change from one humidity value to another may be effected with a minimum of delay, and substantially without interruption of the regulating function.

In carrying out the purposes of the invention, it is proposed to provide within a conduit orenclosed space, containingv the gaseous medium whose moisture content is to be controlled, a spray or equivalent for admitting to said medium a, humidity-aifecting agent, such as steam or water, and to regulate the rate of admission `of said agent` by means subject to the joint influence of a wet-bulb and a dry-bulb thermometer exposed to said medium. It is-proposed that said regulating means shall be embodied in an automatic controlled adapted to regulate the rate of admission of said agent on the basis of tem perature measured by one of lsaid bulbs, and to have the control point of said controller modied under the influence of the other of said bulbs.

tion is applied to the automatic regulation of humidity of a stream of gaseous medium iiowing in an enclosed conduit.

Fig. 2' is a detail of an element of the mechanism shown in Fig. 1.

Referring now to the drawings:

The numeral I0 designates a conduit or pipeline through which is caused to pass a continuous stream of air or other gaseous medium, in a direction as indicated by the arrow A. It is desired to regulate the humidity of said stream, as determined by the relative readings of a dry bulbll and a wet bulb I2, containing expansible or volatile fluids, and adjacently positioned within said conduit in the path of the flowing stream, and said regulation being effected by governing the rate of admission of water, steam, or other moisture-affecting agent from a source i3 through a spray-pipe I4 suitably inserted in said conduit in an upstream direction from said bulbs and including a pneumatically actuated control valve l5 of the reverse-acting class, viz. of that class wherein the valve is opened by an increase in pressure applied to the motor element and closed by a decrease of said pressure.

A measuring instrument I6, preferably in the form of a telemeter transmitter, includes a iiuidpressure-sensitive Bourdon spring or the equivalent I'I, operatively connected to the dry bulb Il by means of a capillary tube i8, whereby the rdeformation of said spring will become a measure of the temperature of the uid within said bulb.

Connected tothe Bourdon spring il', as by linkV I9, is an extended index or pointer-arm 20, pivotally mounted at one extremity, and deflectable at the other, to provide by its deflection a measure of the deformation of the Bourdon spring l1, and thereby of the temperature of the bulb ll. The transmitting element of the instrument |16 may preferably be of the impulseduration class, wherein are developed cyclical electrical impulses having durations varying with the measured magnitude. Such an element is fully set forth and described in U. S. Letters Patent No. 2,214,159, granted to F. B. Bristol September 1-0, 1940. In brief, a scroll-plate 2| having a substantially radial leading edge and a spirally conformed trailing edge is caused to rotate by means of a suitable motor 22 at a constant velocity beneath the pointer-arm 2S, which arm carries on its free extremity a rider, not shown in the drawing, adapted to be engaged by the leading edge of the scroll-plate, and to be released by the trailing edge, whereby with each revolution of the scroll-plate 2| said extremity is deflected alternately forward and backward a short distance perpendicular to its normal plane of displacement. Engageable by the pointer arm 28, to be deflected thereby as the latter is in turn deflected by the scroll-plate, is a rocker plate 25 carried by a shaft 26 positioned transversely of the instrument I6 and pivoted at its extremities for rotation through a small angle about an axis perpendicular to, but not intersecting, the axis of rotation of the scroll-plate. The rocker plate 25 may have upon its surface graduations and indicia, with respect to which the pointer.20-

will provide a measure of the temperature of the bulb II.

Attached to the shaft 26'is an extended arm 21, carrying upon its extremity a ferromagnetic Vane 28 adapted to coact with a permanent mag;- net 29 in controlling the operation of a magnetically operated mercury switch 30. Thus, according to principles fully set forth in said Bristol patent, the timing of operation of said switch will depend directly upon the instants of engagement and disengagement of the pointer arm 2D by the scroll-plate 2I, and, because of the conformation of said scroll-plate, will become a measure of the deflected position of said pointerarm, and therefore of the temperature to which the bulb II is exposed.

A measuring and controlling'instrument 33 includes a fluid-pressure-sensitive Bourdon spring 34 operatively connectedto the wet bulb I2 by means of a capillary tube 35, whereby its deformation will become a measurel of the temperature of the fluid within said bulb. Connected to the Bourdon spring 34, as b'y a link'36, is an extended index or pointer-armA 31, pivotally mounted at one extremity, and deflectable at the other, to provide by its deection a measure cf the deformation of the Bourdon spring 34, and thereby of the temperature of'the wet bulb I2. If desired, there may be included in the structure a stationary scale 38 having thereon graduations and indicia, with respect to which the pointer 31 will provide a measure of the temperature of the bulb I2.

Mounted for angular adjustment about the same axis as that of the pointer-arm 31'is a pneumatic control member 39, having therein one or more jets or orices, not shown in the drawings, whereby to form an element in a control couple, preferably of the type fully set forth and described in U. S. Letters Patent No. 1,880,247, granted to H. L. Griggs and A. R. Mabey October 4, 1932. Attached to the pointer arm 31, and deectable therewith, isa vane member 4B, adapted to coact with the member 39 variably affecting the equivalent area of. theorices therein according to the relative positionv of said control and Vane members. The control instrumentalities associated with the members 39 and 4I] are purely conventional,l and being fully. described both with respect to structure and function, in said Griggs et al. patent, need not here be treated in detail. Aconduit 45 receivesa suitable pressure fluid, e. g., compressed air, from a source 46, applying the same through a constriction 48 tol a conduit 49, and thence to the control member 39 to be exhausted through the jets thereof. A pressure-sensitive bellows member I) is directly connected to the conduit 49, and is adapted to vary its longitudinal dimension with changes of fluid pressure therein. A three-way valve member 5I mounted in juxtaposition to the bellows 50 and adapted for operation thereby, is provided with connection to the conduit 45, and

is connected by means of a conduit 52 to the motor element of the valve I5. Interaction between the bellows 59 and the interior parts of the valve member 5I is such that when said bellows is collapsed the conduit 45 is in communication with the conduit 52, whereby compressed air from the source 46 is applied to the motor element of the valve I5, causing the same to be opened, and as said bellows becomes progressively expanded by increase of pressure therein, communication is correspondingly closed between :the conduits 45 and 52, and the latter exhausted to the atmosphere. The relative positioning of the control members 39 and 4B being suchsthat'a movement toward the left (as shown in the drawing) of the vane 46 with respect to the jetmemberg, corresponding to an increase in temperature at the bulb I2, causes said vane more completely to obstruct the orifices in said member and proportionately to inhibit the escape of air therethrough, it will be seen that such action will result in an increase in pressure within the conduit 49, and-the bellows 5D, whereby to actuate the valve 5'1I in a sense to lower the pressure in the conduit 52, thereby allowing the valve I5 to be closed t0 a corresponding degree. In short, with the structure as thus far set forth, and assuming that the control member 39 is maintained in a fixed position, an increase in temperature as measured by the wet bulb I2 will cause a corresponding decrease of admission of moisture through the valve I5 and spray pipe I4. The basic adjustment -of theY control apparatus is made such that, whatever'theset position of the index 69 with respect to the scale38, the tendency will be for the admission of 'moisture to assume-avalue where-the temperature ofthe wet-b'ulb I2', as'indicated by the pointer 31 on the samelscale-will'be brought into agreement therewith.

Mounted in the instrument 33 is a telemeter receiving mechanism 55 of the impulse-durationresponsive class, and essentially similar to that fully set forth and described in U; S. Letters Patent No. 2,040,918, granted to C. W. Bristol May 19, 1936. Said mechanism, includes a constantspeed motor 56 actuating mechanisms not shown in the drawing, and controlled by the intermittent action of an electromagnet 51, whereby a rotatable shaft or spindle 58 is` caused to seek and assume an angular position dened by the durations of successive operations of said electromagnet. The electromagnet 51 being energized from a suitable electrical source Si] (which may expediently serve alsofas a source of power for the motors 22 and 56) in series with the switch 39 in the instrument I6 and a suitable circuit, it will be seen that the energization and de-energization of said magnet will depend upon the action of said switch as hereinbefore set forth. This, by suitable proportioning, disposition, and adjustment, of correlated elements, the principles of a telemetering system may be incorporated in the associated instruments, and the angular position of the shaft or spindle 58 made representative of the temperature to which the dry bulb I I is exposed.

Attached to the shaft or spindle 58 is a cam member having a conformed periphery and adapted to assume an angular position corresponding to that of said shaft. Attached to the control member 39 is an extended arm 66, carrying a roller 61 and constituting a follower to engage the periphery of said cam'member and be positioned thereby, so that the'angularposition 'Y oi-tll'ey control member `39 will be directly dependent upon that of said cam member. A pointer arm 68 attached to the arm 66 and formingan extension thereof is provided with an index` 69 which cooperates withthe scale 38 in providing an indication of the deiected position` `of the control member 39. The cam 65, being attached to the spindle 58, will assume an angular ,position representative of that ofV the pointer in the instrument I6; and, since the control member 39 is positioned by the arm 66 engaging the periphery of said cam, it follows that the position of said control member will Vbear to the temperature of the dry bulb I I a relationship determined by the conformation of the periphery of the cam, and that the rate of admission of Water or other moistening agent through the `Spay pipe I4 to the conduit I0 will be subject to the joint inuence of the'temperatures of the bulbs II and I2. Y

In order for the apparatus as set forth to regu-- late the humidity of the stream of gaseous medium in the conduit vII! to a predetermined value, it is only necessary to conform the periphery of the cam member G5 to represent said humidity value through the whole range of operating temperatures which will be encountered. The design of such a cam will be better understood by reference to Fig. 2, wherein is shown a cam suited to use with thermometer systems calibrated to ranges between 80 F. and 140 F. The instrument I6 and associated telemetering system being designed so that the full range of the former is linearly represented by a deflection of 240 angular Vdegrees of the shaft 58 and the cam S5, said cam may, if desired, be marked with radial graduations representative of the temperatures within that range. In Fig. 1 is shown an index 'I0 which may expediently be mounted on the stud of the roller 6l, whereby the dry-bulb temperature may be directly read from such graduations marked on the surface of the cam. The

^ radial range of the cam 65 is made such that the angular displacement of the'follower B6 corresponding to said range will be equal to that represented by the scale 38. As thus far described, the typeV of -cam for a particular type of installation would be standard, the dryand wetbulb temperature readings respectively being represented thereon by uniformly spaced polar coordinates; and such cams could be blanked out, and engraved or printed in any desired quantity.

A cam is conformed to control to any predetermined value of relative humidity by the simple expedient of plotting on its graduated surface a polar curve corresponding to that value of humidity which it is desired to maintain. The cam shown in Fig. 2 is shaped to such a curve, based on a polar representation of values taken from the wet-and-dry bulb tables, and corresponding to a value of 99% relative humidity, the wetbulb temperatures being selected on the radial, and the dry-bulb temperature on the circumferential, ordinates. As the cam, deflecting with the shaft 58, will at all times assume angular positions representing the dry-bulb temperatures, the control member 39, being positioned in accord with the conformed prof-lle of said cam, will be set to positions representing the wet-bulb temperatures corresponding to the desired humidity values at said dry-bulb temperatures, and the valve I5 adjusted accordingly in a manner to maintain between said temperatures the preestablished relationship corresponding to the preselected'value of relative humidity. It will be apparent that by substitution for the cam 65 of another cam blanked to the same coordinates, and having its profile conformed to the curve corresponding Ato another' selected humidity value, the` elements of the control apparatus, without any other change, will coact to maintain in the gaseous contents of the conduit I!) a moistur'ercontent represented by said value.

While, in the embodiment hereinabove set forth, the transmitting instrument I6 and the re- Yceiving Vinstrument 33 of a telemetering system have been shown in mutual juxtaposition,V the telemetering elements serving only as a convenientlinkage through which the influence of `Y/the dry-bulb temperature measuring element is superposed upon av control actuated by the wetbulb temperature measuring element, it will ybe obvious that the use of the telemetering principle makes possible the effective utilization of the principle however remote from one another may the two measurements be performed.

The terms and vexpressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modications are possible within the scope of the invention claimed.

I claim:

1. Apparatus for regulating the relative humidity of a gaseous medium, comprising a drybulb thermometer, a wet-bulb thermometer, means comprising a pneumatic control couple for controlling the rate of admission of a humidityaffecting agent to said medium, means connected to one element of said couple for actuating the latter under control of one of said thermometers, and a single cam connected to the other element of said couple for actuating the latter under control of the other of said thermometers, said cam being displaceable in a xed plane only and having an operating portion conformed to ordinates in said plane corresponding respectively to dry-bulb temperatures and to wet-bulb temperatures requisite for maintaining a constant relative humidity at said dry-bulb temperatures.

2. Apparatus for regulating the relative humidity of a gaseous medium, comprising a dry-bulb thermometer, a wet-bulb thermometer; means comprising a control couple for controlling the rate of admission of a humidity-affecting agent to said medium, means connected to one element of said couple for actuating the latter under control of one of said thermometers, and a single cam connected to the other element of said couple for actuating the latter under control of the other of said thermometers, said cam being displaceable in a Xed plane only and having a curved peripheral operating portion conforming to circumferential ordinates in said plane representing temperatures of one of said thermometers and radial ordinates in said plane representing temperatures of the other of said thermometers requisite for maintaining a constant relative humidity at the rst mentioned temperatures.

3. Apparatus for regulating the relative humidity of a gaseous medium, comprising a dry-bulb thermometer, a wet-bulb thermometer, means comprising a control couple for controlling the rate of admission of a humidity-affecting agent to said medium, means connected to one element of said couple for actuating the latter under control of one of said thermometers, a single cam displaceable inasxed plane only and connected to the other element o f saidcouple for actuating the latte-r, andrmeans controlled by the other of said thermometersfor rotating said cam to positionsecorresponding to temperatures represented by said thermometer, said cam having a curved peripheral operating portion conformed to circumferential-ordinates in said plane representing temperatures of said other thermometer Y and radial ordinates in said plane representing temperatures of the thermometer connected to the first mentioned element of the couple requisite for;` maintaining a constantrelative humidity at the rst mentioned temperatures.

4. Apparatusfor regulating. the relative humidity of a gaseous medium, comprising a dry-bulb thermometer; a wet-bulb thermometer, means comprising a control couple for controlling the rate of admission of a humidity-affecting agent to said, medium, means connected to one element ofsaid ,coupleforfactuating the latter under control of the Wet-bulb thermometer, a single cam displaceable in a Xed plane only and connected to the other element of said couple, and means controlled vby the dry-bulb thermometer for Arotating said cam to positions represented by drybulb temperatures, said cam having a curved peripheral operating portion conformed to circumferential ordinates in said plane representing dry-bulb temperatures and radial ordinates in said plane vrepresenting wet-bulb temperatures requisite for maintaining a constant relative humidity at said dry-bulb temperatures.

EVERETT B. JANVRIN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,284,334 Hodge Nov. 12, 1918 1,331,981 Cramer et al Feb. 24, 1920 1,429,973 Roesch Sept. 26, 1922 1,453,688 Milker May 1, 1923 2,084,514 Tuttle et al June 22, 1937 2,128,176 Bast et al Aug. 23, 1938 2,231,568 Gorrie Feb. 11, 1941 

